Role of Arachidonic Acid in Promoting Hair Growth

BACKGROUND: Arachidonic acid (AA) is an omega-6 polyunsaturated fatty acid present in all mammalian cell membranes, and involved in the regulation of many cellular processes, including cell survival, angiogenesis, and mitogenesis. The dermal papilla, composed of specialized fibroblasts located in the bulb of the hair follicle, contributes to the control of hair growth and the hair cycle. OBJECTIVE: This study investigated the effect of AA on hair growth by using in vivo and in vitro models. METHODS: The effect of AA on human dermal papilla cells (hDPCs) and hair shaft elongation was evaluated by MTT assay and hair follicle organ culture, respectively. The expression of various growth and survival factors in hDPCs were investigated by western blot or immunohistochemistry. The ability of AA to induce and prolong anagen phase in C57BL/6 mice was analyzed. RESULTS: AA was found to enhance the viability of hDPCs and promote the expression of several factors responsible for hair growth, including fibroblast growth factor-7 (FGF-7) and FGF-10. Western blotting identified the role of AA in the phosphorylation of various transcription factors (ERK, CREB, and AKT) and increased expression of Bcl-2 in hDPCs. In addition, AA significantly promoted hair shaft elongation, with increased proliferation of matrix keratinocytes, during ex vivo hair follicle culture. It was also found to promote hair growth by induction and prolongation of anagen phase in telogen-stage C57BL/6 mice. CONCLUSION: This study concludes that AA plays a role in promoting hair growth by increasing the expression of growth factors in hDPCs and enhancing follicle proliferation and survival.

Clinical Features and Awareness of Hand Eczema in Korea

BACKGROUND: Hand eczema is one of the most common skin disorders and negatively affects quality of life. However, a large-scale multicenter study investigating the clinical features of patients with hand eczema has not yet been conducted in Korea. OBJECTIVE: To identify the prevalence of various hand diseases, which is defined as all cutaneous disease occurring in hands, and to investigate the clinical features of patients with hand eczema and the awareness about hand eczema in the general population and to compare the prevalence of hand eczema between health care providers and non-health care providers. METHODS: To estimate the prevalence of hand diseases, we analyzed the medical records of patients from 24 medical centers. Patients were assessed by online and offline questionnaires. A 1,000 from general population and 913 hand eczema patients answered the questionnaire, for a total of 1,913 subjects. RESULTS: The most common hand disease was irritant contact dermatitis. In an online survey, the lifetime prevalence of hand eczema was 31.2%. Hand eczema was more likely to occur in females (66.0%) and younger (20~39 years, 53.9%). Health care providers and housewives were the occupations most frequently associated with hand eczema. Winter (33.6%) was the most common season which people experienced aggravation. The 63.0% and 67.0% answered that hand eczema hinders their personal relationship and negatively affects daily living activities, respectively. CONCLUSION: Hand eczema is a very common disease and hinders the quality of life. The appropriate identification of hand eczema is necessary to implement effective and efficient treatment.

A Clinical and Epidemiological Study of Scabies in Korea: A Multicenter Prospective Study / 대한피부과학회지

BACKGROUND: Scabies is an old and common contagious skin disease. The incidence of scabies has decreased through the economic growth of Korea. However, recent outbreaks in medical facilities have created a suspicion that the infection of scabies is an emerging public health problem. OBJECTIVE: We evaluated the epidemiological and clinical aspects of patients diagnosed with scabies in Korea. This prospective study follows the retrospective study already performed by the same authors in 2011. METHODS: A multicenter, prospective study of scabies was performed at 25 hospitals in Korea. We included 914 patients who were diagnosed with scabies. Microscopic examination revealed scabies mites or eggs, or clinical improvement after treatment. Patients were asked to provide information on scabies, especially regarding the contact source, and the physicians examined them. RESULTS: Of the participants, 432 patients were men and 482 were women. Patients aged younger than 10 years and 60~69 years were the most common groups. Scabies more commonly affected patients during the fall and winter. Of the patients, 68.0% were thought to be infected at their homes, followed by nursing homes or hospitals (25.7%), and 31.6% through contact with other patients or, occasionally, staff members, including caregivers. CONCLUSION: We confirmed that scabies is an emerging threat in institutions, especially medical facilities. In addition, we suggest that public and in-hospital education is essential to minimize the problems associated with scabies.

Epidemiological and Clinical Study of Scabies in Korea: Multicenter Retrospective Study / 대한피부과학회지

BACKGROUND: Scabies is one of the common skin diseases observed in developing countries. The incidence of scabies has decreased dramatically since the late 1980s in Korea. However, recent outbreaks in nursing homes or hospitals have been raising public health concerns. OBJECTIVE: We intended to evaluate the epidemiological and clinical aspects of patients diagnosed with scabies in Korea. In particular, we tried to investigate the changing trend of contact sources in our society. METHODS: A multi-center cross sectional study was performed at 25 hospitals in Korea. We included 1,539 patients who were diagnosed with scabies. These patients showed scabies mites or eggs under microscopic examination, or clinical improvement after treatment. Their medical records with information of contact sources were reviewed. RESULTS: Six hundred and ninety-three patients were males and 826 were females. Patients' age from 70 to 79 was the most common followed by patients below 10 years of age. More patients were found in the fall and winter months. 66.7% of patients were thought to be infected at their homes which were situated next to nursing homes or hospitals (23.1%). Place of infection could not be verified in 39.3% of patients. 25.8% of patients were suggested to be infected through contact with medical staff or patients from hospitals or nursing homes. CONCLUSION: We confirmed that the contact sources of scabies are changing in our society; nursing homes and hospitals are emerging sources of infection. The majority of patients are old or very young who are vulnerable to many diseases. Therefore, dermatologists should pay attention to new contact sources and appropriate care of patients.

Pseudomonas Folliculitis Suggestively Caused by Water from Bathing Tub: A Case Report / 대한피부과학회지

Pseudomonas infections can occur from inadequate chemical treatment of water, prolonged exposure to the water source and excessive numbers of bathers in the pool or hot tub. Therefore, pseudomonas folliculitis is also called 'hot tub folliculitis'. We report a 3-year-old boy with Pseudomonas aeruginosa folliculitis suggestively caused by water from the bathing tub of a Hotel. According to the sanitary code of the United States of America, pool staff should regularly check both chlorine and pH levels to prevent swimmers from recreational water infection. However, in Korea, there is no definite regulation regarding chlorine or pH level of recreational water. Thus, we report this issue with a review of the literature.

Principle and Technique for Refinement and Creation of Medical Terminology: Focus on Dermatological Terminologies / 대한피부과학회지

In the Korean language, half of the words originated from Chinese characters, while the other half are from native origins. Since the introduction of Hangul (Korean alphabet consists of 24 characters) with policy by the government after the second-world war, it has dramatically decreased the illiteracy rates within a relatively short period of time in our society. However, since the Japanese colonial period, many professional terminologies which still have its origins from Chinese characters are being used until today. The major issue is that professional terminologies including medical ones are quite difficult for common people to understand, despite their level of education. One aspect is that professional people are using too many sophisticated Chinese characters beyond the limits imposed by the government (1,800 common Chinese characters). In addition, Chinese characters expressed in Hangul are sometimes difficult to understand because of the same pronunciation from different Chinese characters. Since the introduction of medical insurance by the Korean government, most people in our society have benefited cheap medical care. Therefore, easy communication between doctors and patients are becoming mandatory, which is the rationale of developing ideal Korean medical terminology to answer the society's needs. The Korean Medical Association has encouraged the developments of simple and elegant medical terminologies for a very long time, and dramatic refinements of them have been made for the past 20 years. However, in reality, the majority of terminologies are still not unified because of strong conflicts between conservatism and liberalism toward the changes. The author recently published a monograph with an anatomist and a linguist, which contains the principles and techniques for refinement and creation in order to make easy and elegant medical terminologies with plenty of examples. From the article, the author intended to introduce many examples including conflicts solving strategies in the field of dermatology.

Gene mapping study for constitutive skin color in an isolated Mongolian population

To elucidate the genes responsible for constitutive human skin color, we measured the extent of skin pigmentation in the buttock, representative of lifelong non-sun-exposed skin, and conducted a gene mapping study on skin color in an isolated Mongolian population composed of 344 individuals from 59 families who lived in Dashbalbar, Mongolia. The heritability of constitutive skin color was 0.82, indicating significant genetic association on this trait. Through the linkage analysis using 1,039 short tandem repeat (STR) microsatellite markers, we identified a novel genomic region regulating constitutive skin color on 11q24.2 with an logarithm of odds (LOD) score of 3.39. In addition, we also found other candidate regions on 17q23.2, 6q25.1, and 13q33.2 (LOD > or = 2). Family-based association tests on these regions with suggestive linkage peaks revealed ten and two significant single nucleotide polymorphisms (SNPs) on the linkage regions of chromosome 11 and 17, respectively. We were able to discover four possible candidate genes that would be implicated to regulate human skin color: ETS1, UBASH3B, ASAM, and CLTC.

Clinical Characteristics and Prognostic Factors in Early-Onset Alopecia Totalis and Alopecia Universalis

Alopecia totalis (AT) and alopecia universalis (AU), severe forms of alopecia areata (AA), show distinguishable clinical characteristics from those of patch AA. In this study, we investigated the clinical characteristics of AT/AU according to the onset age. Based on the onset age around adolescence ( or = 13 yr), 108 patients were classified in an early-onset group and the other 179 patients in a late-onset group. We found that more patients in the early-onset group had a family history of AA, nail dystrophy, and history of atopic dermatitis than those in the late-onset group. These clinical differences were more prominent in patients with AU than in those with AT. In addition, significantly more patients with concomitant medical disorders, especially allergic diseases were found in the early-onset group (45.8%) than in the late-onset group (31.2%). All treatment modalities failed to show any association with the present hair condition of patients. In the early-onset group, patients with AU or a family history of AA showed worse prognosis, whereas this trend was not observed in the late-onset group. Systemic evaluations might be needed in early-onset patients due to the higher incidence of comorbid diseases. It is suggested that patients with AU or family history of AA make worse progress in the early-onset group than in the late-onset group.

Physiological Characteristics of Skin of Normal Mongolian Subjects Determined by Non-invasive Bioengineering Methods / 대한피부과학회지

BACKGROUND: Physiological parameters of the skin measured by non-invasive methods have been considerably developed. It is known that there are some differences in physiologic parameters between different races. OBJECTIVE: The purpose of this study is to understand the differences between the races. METHODS: A total of 757 Mongolian participated in this study. All subjects had no major history of skin diseases requiring medical treatment. Several instruments were used such as Sebumeter, Corneometer, Mexameter for measuring sebum excretion rate, values of capacitance, melanin index and erythema index respectively. These were measured on various areas of the skin such as cheek, forehead, palm, outer arm, inner arm, back and buttock. RESULTS: The sebum excretion rates showed higher in males than in females on the cheek and forehead in Mongolian. However, they showed higher in the females on the palm. There were good correlation between the skin sebum level and the capacitance in males and females. The melanin index and erythema index showed higher in males than in females at all sites. When we compared this with the data published in other countries, many data were similar to Korean rather than a western country's. However, the capacitance data were lower than those of Korean. CONCLUSION: Although, this study has some limit for direct comparison between each race, our results can be used as basic data for the comparison between Mongolian and other races in the future.

TRUE Test in Patients with Contact Dermatitis: A Multicenter Study / 대한피부과학회지

BACKGROUND: The TRUE test is a commercially available ready-to-apply patch test widely used in many countries, but no large-scale study is available on the TRUE test in Korea. OBJECTIVE: The purpose of this study was to analyze the type, frequency, and changes in the common contact allergens in Korea using the TRUE test. METHODS: From January 2009 to March 2010, TRUE tests were performed on patients with contact dermatitis at the Departments of Dermatology of 15 hospitals. The epidemiological findings of patients, and the results of the patch tests were analyzed. RESULTS: In total, 795 patch tested cases (246 males, 549 females) were compiled and analyzed. The oldest age distribution was the third decade in both males and females, and housewives and office-workers were the most common jobs, comprising 29.7% and 19.8% of the occupations, respectively. Overall, 65.1% of patients had at least one positive reaction, and the most common allergens were nickel sulfate (34.1%), thimerosal (12.6%), cobalt chloride (11.1%), and p-phenylenediamine (8.4%), in order of frequency. A univariate analysis of multiple variables including age, gender, occupation, and affected sites was conducted and a comparison with a previous multicenter study was also analyzed. CONCLUSION: These results provide the basis for use of the TRUE test in patients with contact dermatitis in Korea.

Chemical Leukoderma Improved by Low-dose Steroid Pulse Therapy

Chemical leukoderma occurs due to the toxic effect of a specific chemical preceding allergic contact dermatitis. The mechanism is either destruction or inhibition of melanocytes by the offending substance. Clinicohistopathologically, no absolute criteria can differentiate chemical leukoderma from vitiligo. However, chemical leukoderma can be diagnosed clinically by a history of repeated exposure to a known or suspected depigmenting agent at the primary site. There is no agreed treatment guideline for chemical leukoderma. We report a healthy 51-year-old man who had multiple hypopigmented macules and patches on his face, neck, arms and legs after exposure to occupationally related chemicals. The lesions were recalcitrant to topical corticosteroids, but they showed much improvement after 3 cycles of systemic steroid pulse therapy. We suggest this therapy may be a good treatment option for chemical leukoderma.

Live Interactive Teledermatologic Consultation: Clinical Evaluation and the Patients' Satisfaction / 대한피부과학회지

BACKGROUND: Telemedicine is broadly defined as using telecommunication technology to transfer medical information. Teledermatology is defined as using telemedicine in the field of dermatology, and this can be divided into a storage-and-forward system and a live interactive system. The latter uses video-conferencing equipment and it is known to be more useful than the former. However, there have been few studies on live interactive teledermatologic consultation in Korea. OBJECTIVE: We wanted to describe and quantify teledematologic consultation and to assess patients' satisfaction with the live interactive consultation by using a questionnaire. METHODS: We retrospectively reviewed the records of the patients who were consulted through the teledermatologic system. To assess patients' satisfaction with the live interactive teledermatologic consultation, we asked the patients to complete a questionnaire after the consultation. RESULTS: A total of 98 patients were consulted for 112 skin problems. The most frequent skin problem was eczematous diseases (33.9%), followed by infectious diseases (25.0%). Concerning the treatment efficacy, 90.7% of the patients experienced improvement of their initial symptom. Only one main diagnosis was recorded for 64.3% of the cases, and one main diagnosis with one other possible diagnosis to be differentiated was recorded for 30.4% of the cases. For the aspect of the technical quality, 66.1% of the patients were satisfied or very satisfied with the performance of the instruments for live interactive communication. In addition, half of the patients were satisfied or very satisfied with the teledermatologic consultation, and 59.7% of the patients answered that they would use teledermatologic consultation system again if another skin problem develops. CONCLUSION: With its good performance, teledermatologic consultation seems to be helpful and satisfactory for the patients who are unable to visit the dermatologic out-patients clinic.

A Study of the Patch Test Results with Preservative Antigens for Patients with Suspected Cosmetic Contact Dermatitis / 대한피부과학회지

BACKGROUND: Preservatives are important contact allergens. However, any reports that have focused on them are relatively scanty in Korea. OBJECTIVE: The aim of this study is to investigate the prevalence of preservative allergy in patients with suspected cosmetic contact dermatitis. METHODS: We retrospectively reviewed the patch test results and medical recordings of the patients who were suspected of having cosmetic contact dermatitis from January 2003 to December 2008 and who visited Seoul National University Hospital. A total of 330 patients (males: 69, females: 261) were enrolled in our study and the medical records included the patients' demographic information, the site of contact dermatitis, the past dermatologic diseases and the duration of the disease. We used 30 cosmetic preservative antigens. RESULTS: The mean age of the patients was 42.5 years and the most common age of the group with contact dermatitis was in the forties. The most prevalent site for contact dermatitis was the face (60.3%). Forty nine patients (14.8%) had a past history of atopic dermatitis. A hundred thirty nine patients (42.1%) showed at least one positive patch test result. Thiomerosal showed the highest patch test rate (10.6%), followed by cocamidopropylbetaine (8.1%), Euxyl K400 (7.8%), Dodecyl gallate (6.9%) and Octyl gallate (6.6%). CONCLUSION: As the positive rate of a patch test with preservative antigens was relatively high, certain preservative antigens contained in the cosmetic series should be included in the patch test for patients with suspected cosmetic contact dermatitis.

Acidic pH-activated Cl- Current and Intracellular Ca2+ Response in Human Keratinocytes

The layers of keratinocytes form an acid mantle on the surface of the skin. Herein, we investigated the effects of acidic pH on the membrane current and [Ca2+](c) of human primary keratinocytes from foreskins and human keratinocyte cell line (HaCaT). Acidic extracellular pH (pHe< or =5.5) activated outwardly rectifying Cl- current (I(Cl,pH)) with slow kinetics of voltage-dependent activation. I(Cl,pH) was potently inhibited by an anion channel blocker 4,4`-diisothiocyanostilbene-2,2`-disulphonic acid (DIDS, 73.5% inhibition at 1micrometer). I(Cl,pH) became more sensitive to pHe by raising temperature from 24degrees C to 37degrees C. HaCaT cells also expressed Ca2+ -activated Cl- current (I(Cl,Ca)), and the amplitude of I(Cl,Ca) was increased by relatively weak acidic pHe (7.0 and 6.8). Interestingly, the acidic pHe (5.0) also induced a sharp increase in the intracellular [Ca2+] (delta[Ca2+](acid)) of HaCaT cells. The delta[Ca2+](acid) was independent of extracellular Ca2+, and was abolished by the pretreatment with PLC inhibitor, U73122. In primary human keratinocytes, 5 out of 28 tested cells showed delta[Ca2+](acid). In summary, we found I(Cl,pH) and delta[Ca2+](acid) in human keratinocytes, and these ionic signals might have implication in pathophysiological responses and differentiation of epidermal keratinocytes.

The Long Term Efficacy and Relapse Rate of Itraconazole Pulse Therapy Versus Terbinafine Continuous Therapy for Toenail Onychomycosis: a 96-week follow-up study / 대한의진균학회지

No abstract available.

Promotive Effect of Minoxidil Combined with All-trans Retinoic Acid (tretinoin) on Human Hair Growth in Vitro

Minoxidil induces hair growth in male pattern baldness and prolongs the anagen phase. All-trans retinoic acid (ATRA) has been reported to act synergistically with minoxidil in vivo: they can enhance more dense hair regrowth than either compound alone. We evaluated the effect of minoxidil combined with ATRA on hair growth in vitro. The effect of co-treatment of minoxidil and ATRA on hair growth was studied in hair follicle organ culture. In cultured human dermal papilla cells (DPCs) and normal human epidermal keratinocytes, the expressions of Erk, Akt, Bcl-2, Bax, P53 and P21 were evaluated by immunoblot analysis. Minoxidil plus ATRA additively promoted hair growth in vitro, compared with minoxidil alone. In addition, minoxidil plus ATRA elevated phosphorylated Erk, phosphorylated Akt and the ratio of Bcl-2/Bax, but decreased the expressions of P53 and P21 more effectively than by minoxidil alone. Our results suggest that minoxidil plus ATRA would additively enhance hair growth by mediating dual functions: 1) the prolongation of cell survival by activating the Erk and Akt signaling pathways, and 2) the prevention of apoptosis of DPCs and epithelial cells by increasing the ratio of Bcl-2/Bax and downregulating the expressions of P53 and P21.

The Analysis of the Expression of TGF-beta in Human Hair Follicles in vivo / 대한피부과학회지

BACKGROUND: Although it is well known that transforming growth factor beta (TGF-beta) may induce catagen change of hair follicles and inhibit hair growth, it is still unclear which subtype of TGF-beta and its specified receptor might be expressed in human hair follicles of androgenetic alopecia (AGA) patients. OBJECTIVE: To delineate precise expression of TGF-beta subtype in human hair follicles of androgenetic alopecia patients. METHODS: Immunohistochemical studies were performed on paraffin sections of human hair follicles by applying type 1, 2, and 3 TGF-beta antibodies and type I and II receptor antibodies. We ascertained the expression of TGF-beta subtype in hair follicles of androgenetic alopecia patients. We also compared the expression pattern of each type of TGF-beta receptor. We evaluated the change of TGF-beta expression of hair follicles in the catagen phase. RESULTS: TGF-beta1 was well-expressed in the outer area of the inner root sheath (IRS) or dermal connective sheath area. TGF-beta2 was commonly expressed in the inner 1/2 of the outer root sheath (ORS). TGF-beta3 was expressed in the hair cortex, IRS, and cuticle in normal hair follicles obtained from both the vertex and occipital area. On the contrary, in specimens from AGA, the enhanced expression of type 2 TGF-beta or type II receptor was observed in the vertex area (bald) compared to the occipital area (non bald). When the expression patterns of TGF-beta 1, 2, and 3 were compared between anagen and catagen phases, TGF-beta2 and 3 were positively expressed in the epithelial strands and secondary hair germs in the catagen phase. The immunoreactivities of TGF-beta 1 and 2 were intensified in the ORS areas of the catagen phase. CONCLUSION: The expression of type 1, 2 TGF-beta and type I and II receptors in follicular epithelial cells might be related to catagen induction and development of androgenetic alopecia of human hair in vivo.

The Efficacy and Safety of AP-FHG0604T on Female Pattern Hair Loss: A Randomized Double-blind Placebo-controlled Clinical Trial / 대한피부과학회지

BACKGROUND: Hair loss is a very common disorder and the number of patients is known to be increasing. Female pattern hair loss (FPHL) is not only a medical problem but also a very severe psychosocial problem for many female patients. Anti-androgen drugs, mineral supplements and topical minoxidil have all been used for the treatment of FPHL. However they do not always achieve successful results and there is still much need for more effective therapy. OBJECTIVE: The purpose of this 18-week, double-blind, placebo-controlled, randomized clinical trial was to investigate the efficacy and safety of a new topical agent, AP-FHG0604T, in the treatment of FPHL. METHODS: A total of 33 women with FPHL (mean age: 33.4 years old) applied either a topical AP-FHG0604T solution (n=17), or placebo (vehicle for AP-FHG0604T solution; n=16) twice daily. Efficacy was evaluated by phototrichogram, investigator's photographic and patient's subjective assessments. All adverse effects were reported during the study. RESULTS: After 18 weeks of therapy, topical AP-FHG0604T treatment showed a significant improvement compared to baseline values of total hair count, non-vellus hair count, and linear hair growth rate. In the placebo group, non-vellus hair count and ratio of anagen hair significantly decreased. The change rates of total hair count and non-vellus hair count in the AP-FHG0604T group were significantly higher than those in the placebo group. Neither investigator's photographic assessments nor patient's subjective assessments of hair growth showed statistically significant differences between the AP-FHG0604T group or the placebo group. Some patients who used AP- FHG0604T complained of local irritation during the study, but the irritation was so mild that they did not need any treatment for this. CONCLUSION: We conclude that AP-FHG0604T is a safe and efficient topical agent which can be used as another treatment of choice for FPHL, as shown by objective assessment with phototrichogram.

Role of Staphylococcal Superantigen in Atopic Dermatitis: Influence on Keratinocytes

Staphylococcus aureus may perform an crucial function in atopic dermatitis (AD), via the secretion of superantigens, including staphylococcal enterotoxins (SE) A or B, and toxic shock syndrome toxin-1 (TSST-1). Dysregulated cytokine production by keratinocytes (KCs) upon exposure to staphylococcal superantigens (SsAgs) may be principally involved in the pathophysiology of AD. We hypothesized that lesional KCs from AD may react differently to SsAgs compared to nonlesional skin or normal skin from nonatopics. We conducted a comparison of HLA-DR or CD1a expression in lesional skin as opposed to that in nonlesional or normal skin by immunohistochemistry (IHC). We also compared, using ELISA, the levels of IL-1alpha, IL-1beta, and TNF-alpha secreted by cultured KCs from lesional, nonlesional, and normal skin, after the addition of SEA, SEB and TSST-1. IHC revealed that both HLA-DR and CD1a expression increased significantly in the epidermis of lesional skin versus nonlesional or normal skin in quite a similar manner. IL-1alpha, IL-1beta, and TNF-alpha secretion was also significantly elevated in the cultured KCs from lesional skin after the addition of SsAgs. Our results indicated that KCs from lesional skin appear to react differently to SsAgs and increased proinflammatory cytokine production in response to SsAgs may contribute to the pathogenesis of AD.

Hair Cycle-associated Changes of the Immunological Markers in Human Hair Follicles / 대한피부과학회지

BACKGROUND: The immunological characteristics of human hair follicles with the hair growth cycle have not yet been fully elucidated. It is suggested that expressional changes of the immunological markers in the hair cycle may play a role in catagen induction of the hair follicles. OBJECTIVE: To analyze the immunological features in human hair follicles according to the hair growth cycle. METHODS: An immunohistochemical study was performed on frozen sections of human hair follicles using major histocompatibility complex (MHC) class I & II, CD1a, Fas, Fas ligand, and ACTH antibodies. We then compared the hair cycle-associated expressional changes of these markers. RESULTS: Human anagen hair bulbs showed very low level of the MHC class I expression. In catagen transition, enhanced expression of the MHC class I was observed in the proximal hair follicles. This change may correspond to regressing morphological change of hair follicles in the catagen transition. Some changes in the expression of MHC class II and Fas/FasL in hair follicles were also observed in catagen transition. CONCLUSION: Downregulation of MHC class I expression in the proximal epithelium of the anagen hair bulb may contribute to so-called 'immune privilege'. In catagen transition, the expression of MHC class II and Fas/FasL, together with upregulation of MHC class I, might be related to morphologic changes of the hair follicle.